Citrus rootstock named &#39;UFR-5&#39;

ABSTRACT

‘UFR-5’ is a new and distinct allotetraploid citrus rootstock for tree size control and improved disease resistance. ‘UFR-5’ has shown a positive reaction to the Huanglongbing disease (HLB, or citrus greening disease) in multiple experimental field trials. Scion trees grafted on this rootstock show a reduced frequency of infection and reduced disease symptoms once infected as compared to commercial diploid rootstocks.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of United States Provisional Application No. 61/942,574, filed Feb. 20, 2014, herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Latin name of the genus and species of the plant claimed: Citrus reticulata/Citrus paradisi+Citrus grandis×Citrus sinensis+Poncirus trifoliata

Variety denomination: ‘UFR-5’

The present invention relates to a new and distinct variety of citrus rootstock named ‘UFR-5’. The Plant Improvement Team in Lake Alfred, Fla. has pioneered the development and testing of allotetraploid citrus rootstocks. ‘UFR-5’ (identified as White #4 in field trials) is an allotetraploid zygotic hybrid derived from a conventional cross of two somatic hybrids previously produced by protoplast fusion. The somatic hybrid seed parent is ‘Nova’ mandarin hybrid+Hirado Buntan pummelo (zygotic seedling), and the somatic hybrid pollen parent is Succari sweet orange+Argentine trifoliate orange.

BRIEF SUMMARY OF THE INVENTION

‘UFR-5’ was selected as a potential citrus rootstock on the basis of its positive reaction to Huanglongbing disease (HLB, or citrus greening disease) in multiple experimental field trials. Scion trees grafted onto this rootstock showed a reduced frequency of infection and reduced disease symptoms once infected when compared to other commercial diploid rootstocks. Although scion trees grafted onto ‘UFR-5’ grow off quickly, the trees remain small-medium in size, comparable to scion trees grafted onto Swingle citrumelo rootstock. Scion trees are small in size when grown on flatwoods soils. ‘UFR-5’ is seedy and polyembryonic, making it suitable for standard nursery propagation practices for uniform liner production. ‘UFR-5’ has shown tolerance to Diaprepes/Phytophthora complex in greenhouse tests (Grosser et al., 2003). ‘UFR-5’ produces high quality sweet orange fruit. Long-term performance of trees on this rootstock selection is unknown. Yield and fruit quality data is limited, but 3 years of data from young trees (the St. Helena project, see Table 1) indicates good productivity and fruit quality. Tolerance to citrus blight is also unknown, but under investigation. True-to typeness of UFR-5 through asexual reproduction was demonstrated by topworking a Swingle citrumelo rootstock in Osceola county, Florida. Seeds from this tree and the original tree are predominantly of nucellar origin and produce true-to-type seedlings.

TABLE 1 Rootstock Data from 5-year old trees in the St. Helena trial-Dundee, FL. Yield Boxes/Tree Cumulative Lbs Solids/Box 2011 2012 2013 Yield Scion Type Rootstock 2012 2013 (35 mo.) (47 mo.) (59 mo.) (Boxes) VALQUARIUS Som. Hyb. ‘UFR-6’ 5.64 5.43 0.5 0.78 1.94 3.22 VERNIA Som. Hyb. ‘UFR-6’ 5.67 6.01 0.4 0.63 1.41 2.44 VALQUARIUS Tetrazyg ‘UFR-1’ 5.5 4.87 NS 0.72 2.23 2.95 VERNIA Tetrazyg ‘UFR-1’ 5.61 6.28 0.31 0.67 1.33 2.31 VERNIA Tetrazyg ‘UFR-2’ 5.47 5.93 0.35 0.25 1.38 1.98 VALQUARIUS Tetrazyg ‘UFR-2’ 4.57 5.37 NS 0.75 1.73 2.48 VALQUARIUS Tetrazyg ‘UFR-3’ 4.84 5.05 NS 0.81 1.97 2.78 VERNIA Tetrazyg ‘UFR-3’ 5.46 5.82 0.37 0.38 1.82 2.57 VERNIA Tetrazyg ‘UFR-4’ 5.79 6.07 0.54 0.71 1.73 2.98 VALQUARIUS Tetrazyg ‘UFR-4’ 4.65 5.07 NS 0.65 1.59 2.64 VALQUARIUS Tetrazyg ‘UFR-5’ 5.76 5.72 0.33 0.56 1.80 2.69 VERNIA Tetrazyg ‘UFR-5’ 5.89 5.34 0.42 0.25 1.93 2.60 VALQUARIUS Diploid FG 1731 5.83 6.81 NS 0.68 2.20 2.88 VALQUARIUS Diploid FG 1733 5.12 5.63 NS 0.67 2.77 3.44 VERNIA Diploid SWINGLE* 5.11 5.79 0.33 0.85 1.08 2.26 VALQUARIUS Diploid SWINGLE* NS 5.61 NS NS 1.50 1.50 VERNIA Diploid CLEO* 4.79 5.51 NS 0.50 0.83 1.33 VALQUARIUS Diploid CLEO* NS 5.21 NS NS 1.7 1.7 VERNIA Diploid R. LEMON* 3.67 na NS 0.78 na 0.78 VALQUARIUS Diploid VOLK* NS 4.12 NS NS 2.58 2.58 VERNIA Diploid VOLK* 3.6 4.73 0.4 1.13 0.83 2.36 VALQUARIUS Diploid KUHARSKE* NS 5.75 NS NS 2.2 2.2 VERNIA Diploid KUHARSKE* 4.34 5.83 0.15 0.75 1.08 1.98 NS-not significant fruit; na-data not available; *-control commercial rootstock One box contains approximately 90 lbs. fruit.

BRIEF DESCRIPTION OF THE DRAWINGS

‘UFR-5’ is illustrated by the accompanying photographs, which show the tree's form, foliage, and fruit. The colors shown are as true as can be reasonably obtained by conventional photographic procedures. The photographs are of a tree approximately 11 years old. All figures were taken in the fall of 2013.

FIG. 1.—Shows a close-up of the nearly mature fruits with the rind and cross-sectional view of the fruit when cut in the center.

FIG. 2.—Shows the overall mature plant growth habit.

FIG. 3.—Shows nearly mature fruits hanging on the tree.

FIG. 4.—Shows a close-up of leaves and nearly mature fruits.

FIG. 5.—Shows a close-up of nearly mature fruits.

FIG. 6.—Shows a close-up of seeds from nearly mature fruit.

DETAILED BOTANICAL DESCRIPTION

The following detailed description sets forth the distinctive characteristics of ‘UFR-5’. The colors (except those in common terms) are described from the R.H.S. Colour Chart published by The Royal Horticultural Society in London (second edition), in association with the Flower Council of Holland.

-   Phenotypic description of Citrus reticulata/Citrus paradisi+Citrus     grandis+Citrus sinensis+Poncirus trifoliata ‘UFR-5’: -   Classification:     -   -   Botanical.—[Citrus reticulata hybrid (Clementine             mandarin×Orlando tangelo) Citrus reticulata×Citrus             paradisi)+Citrus grandis]×[Citrus sinensis+Poncirus             trifoliata (trifoliate orange)].         -   Common name.—Complex allotetraploid ‘tetrazyg’ rootstock             hybrid. -   Parentage:     -   -   Female parent.—‘Nova’ mandarin+Hirado Buntan pummelo             (zygotic seedling) somatic hybrid (unpatented).         -   Male parent.—Succari sweet orange+Argentine trifoliate             orange; somatic hybrid (unpatented). -   Tree:     -   -   Ploidy.—Tetraploid.         -   Size.—Medium-large.         -   Height.—4.62 meters.         -   Tree spread.—3.8 to 4.0 meters.         -   Vigor.—Moderately vigorous.         -   Density.—Canopies are moderately dense.         -   Form.—The tree is round-shaped with lateral and upright             branches.         -   Growth habit.—Both upright and lateral growth with a medium             angle. -   Trunk:     -   -   Trunk diameter.—21 cm in diameter at 30 cm above the ground             on a 16-year-old tree.         -   Trunk texture.—Rough.         -   Trunk bark color.—RHS 198A (greyed-green); irregularly             striated with RHS 197A (greyed-green). -   Branches:     -   -   Crotch angle.—First crotch forms 40- to 45-degree angle,             middle crotch forms a 85-degree angle.         -   Branch length.—Branch reaches 4.0 meters from the first             crotch to the tip of the branch.         -   Branch texture.—Relatively rough with small thorns or             spines.         -   Branch color (shoots from previous flush, hardened and 4 to             5 mm in diameter).—RHS N137A (green). -   Leaves:     -   -   Size (lamina average).—Length: 106.7 mm Width: 70 mm L/W             ratio: 1.51.         -   Thickness.—Thicker than average diploid citrus rootstock             hybrids.         -   Type.—Simple.         -   Shape.—Elliptical.         -   Apex.—Retuse.         -   Base.—Acute to sub-obtuse.         -   Margin.—Entire and slightly undulate.         -   Surface.—Upper surface: Glabrous Lower surface: Medium veins             that are pinnately netted.         -   Color.—Upper surface (adaxial): RHS 137A (green) Lower             surface (abaxial): RHS 146A (yellow-green).         -   Petiole.—Shape: Brevipetiolate (shorter than leaf lamina);             junction between petiole and lamina is articulate Width             (petiole wing): Narrow, with obvious medium broaden wing             Shape (petiole wing): Obovate Length: 13.5 to 19.5 mm Width:             4 to 9 mm Color: RHS 137A (green). -   Flowers and flower buds:     -   -   Type.—Hermaphrodite.         -   Bearing.—Flowers grow from leaf axillaries and leaf             terminals singly and in small clusters; most single flowers             grow from leaf axillaries.         -   Flower bud size.—Shape: Initial visible flower bud has a             round ball shape; mature flower bud has an elongated olive             shape.         -   Flower petals.—Shape: Flat, spatula-shaped Apex shape:             Smooth, acute-shaped Base shape: Even obtuse Margin: Smooth.         -   Flower sepal.—Shape: Delta-shaped with an acute angle at the             apex Apex shape: Triangle-shaped Margin: Smooth.         -   Fragrance.—Fragrant/Moderately fragrant.         -   Reproductive organs.—Fertility: Appears self-fertile Pollen             amount: Abundant/Moderate amount Pollen color (general):             Bright-yellow Ovary shape: Oval-shaped. -   Fruit:     -   -   Size.—Uniform.         -   Height.—79.3 to 81.2 mm on average.         -   Width.—82 to 86.5 mm on average.         -   Average weight (per individual fruit).—263 grams.         -   Shape.—Round and earth shaped.         -   Shape (cross-section).—Round.         -   Apex.—Truncated with slight dent.         -   Apex cavity diameter.—N/A.         -   Base cavity diameter.—5.4 to 5.7 mm.         -   Base.—No neck.         -   Harvesting.—Fruit can be harvested from October through             December in Florida.         -   Fruit stem (short stem connecting the fruit).—Length: 11.6             mm Diameter: 5.1 mm Color: RHS 198A (greyed-green) with RHS             137C (grey-green) strip. -   Rind:     -   -   Adherence.—Adherence between albedo (mesocarp) and flesh             (endocarp) is medium. The adherence is evenly distributed             from base to apex.         -   Thickness.—3.4 to 4.8 mm on average.         -   Texture.—Smooth.         -   Color.—Flavedo (epicarp): Ranges between RHS 151B             (yellow-green) to RHS 151 A (yellow-green) Albedo             (mesocarp): RHS 157D (green-white).         -   Stylar end.—Closed.         -   Rind oil cell density.—62 oil cells/square cm. -   Flesh:     -   -   Number of segments.—Between 7 and 8 segments per fruit on             average.         -   Segment walls.—Firm with sufficient strength to maintain             integrity as separated.         -   Juice.—Abundant.         -   Color.—Uniformly RHS 11 C (greyed-yellow).         -   Texture.—Medium soft.         -   Vesicles.—Length: Arranged from 11.5 to 12.2 mm on average             Diameter (thickness): 3.8 to 4.2 mm on average.         -   Eating quality.—N/A.         -   Juice index.—         -   Soluble solids (average).—10 Brix. -   Seeds:     -   -   Type.—Polyembryonic.         -   Number.—Ranges from 24 to 34.         -   Shape.—Seed shapes are not uniform. Normal seeds are mostly             ventricose/swollen-shaped and clavate club shaped.         -   Size.—Length: 17 to 18.2 min Width: 8 to 8.9 mm.         -   Seed coat color.—Outer Surface: RHS 155B (white) and             wrinkled Inner surface: RHS 146B (greyed-orange) Cotyledon             color: RHS 145D (yellow-green). -   Resistance to disease: ‘UFR-5’ rootstock was selected on the basis     of its positive reaction to HLB disease (huanglongbing or citrus     greening disease) in multiple field trials. Trees on this rootstock     show a reduced frequency of infection and reduced disease symptoms     once infected as compared to commercial diploid rootstocks. 

What is claimed is:
 1. A new and distinct citrus rootstock cultivar as illustrated and described herein. 